Outcomes research has demonstrated that the quality of pediatric surgical care varies across centers in the United States. Understanding the key drivers of this variation and ultimately how to improve care are critical questions facing clinicia-scientists in pediatric cardiac critical care and cardiac surgery. This proposal seeks to elucidate the underlying reasons for variation in quality of care after pediatric cardiac surgery while providing the career development candidate with a very rich research training and mentorship experience. The research proposal focuses specifically on perioperative mortality for the 20,000 children and young adults who require surgery for pediatric and congenital heart disease each year. Variation in outcomes between hospitals suggests opportunities to reduce potentially avoidable deaths in this vulnerable population. The proposal's research aims include (1) determining the clinical epidemiology of perioperative mortality and the cause- specific mortality that drives variation in hospital performance; (2) analyzing the system and organizational factors that associate with better outcomes; and (3) determining the specific processes of care that underlie hospital performance. This project, the multidisciplinary mentorship team, and the research environment are ideally suited to address the career goals and educational needs of the candidate, Michael G. Gaies, MD, MPH. Dr. Gaies is a board-certified pediatric cardiologist with clinical and scientific interests in patient-centered outcomes research in the pediatric cardiac intensive care unit setting. His prior research experience in studying pediatric cardiac surgical outcomes and interventions to optimize cardiac critical care has prepared him for this proposal. However, he will need additional training to achieve his career goal of improving perioperative care via an international quality-improvement consortium. His educational goals to develop expertise in advanced statistical methods for comparing hospital performance and implementation science are feasible as described in the grant's educational plan with the assistance of his highly accomplished mentorship team. The educational program includes graduate-level coursework, structured seminars, project-based learning, and interaction with international experts in measuring the quality of surgical care. In summary, this research proposal, mentorship team, educational plan, and the overall institutional environment will lay the groundwork for Dr. Gaies to become an innovative, independent scientist capable of translating his findings into improved care for children with critical cardiovascular disease.